VAR in itself is nothing but a tool. Operators aren't that great in La Liga, but then there are some rotten apples in other leagues too. I think fundamentally there are protocol issues in La Liga, which will not be resolved by VAR implementation. Basically I fear VAR to be used much more like it was in Spurs-Rochdale game a few days ago where the ref checked his earpiece to see if the goal was legal EVERY. TIME. Ridiculous.
La Liga referees should probably be far more leaning to do justice and check things too many times than necessary just because of the amount of scrutiny they are under. Spaniards won't take well to that.
RFEF really needs to meet with representatives from other leagues to change their ref training. I don't watch that much Bundesliga or Serie A, but you don't hear of too many problems resulting from VAR, or refereeing in general. But then again I don't pay that much attention to these leagues.
Basically I have zero trust in VAR to improve the league next season. If anything it'll be a test of patience for the viewers. It'll be useful for offsides and so, but fouls will still be super contentious and interruptions to the flow of the game will infuriate the masses initially.